VEX

Natsura's extension points share one language. A custom effector, a wrangle in the growth graph and a custom map are all VEX, and the shipped effectors and maps are built the same way, so opening one up is the quickest way to learn the pattern.

Custom effectors

An effector writes a direction per point, and the node it is added to applies that direction through a response mode (attract, repel, flatten, level and so on) and a strength you can map. Effectors covers the model and the shipped effectors.

When none of those give you the field you want, use the Effector node (experimental) and write the direction in its VEXpression from any attribute the growth carries. Once written, it behaves like a built-in effector. The conventions it has to follow, such as scoping lookups to its own points, are on the Effector page.

So a custom effector is mostly a VEX problem: read the attributes you care about, decide on a direction, write it out.

Wrangles

The Wrangle runs VEX inside the growth graph, on the growing tips during the simulation. Use it for anything the core nodes don't express: writing a custom attribute, gating growth on a condition, or computing a value of your own, such as the distance to an object in your scene (wired into the Wrangle's third input) or an age that counts during growth, for a Map or Switch to read.

A wrangle's job is usually to write an attribute, not to make geometry. Read what the internodes already carry (u, height, generation, anything written upstream, or attributes from your source points), compute the value, write it back, and let maps and switches use it.

Custom maps

Mapping turns a parameter into a value computed per point from an attribute. To add behaviour of your own, write a map in VEX.

Map Wrangle (experimental) writes a map in VEX. It takes up to four inputs as floats, in0 to in3, and you assign the result to out. Use it like any other map node in a chain.

To give a node of your own mappable parameters, so it can be driven by maps like the shipped nodes, use Mapping Template. It is hidden from the Tab menu in 0.7.3; Make Your Own Tools says how to place it.

Status

Worked examples for each of these are still to come: a custom effector that bends growth towards a curve, common wrangle patterns, and a map written with Map Wrangle. In the meantime, the shipped effectors, such as Gravity Effector, open with a note inviting you to read and adapt their code.